The continued evolution of communication networks must often overcome the basic challenges of advancing technical solutions while at the same time taking into consideration the past and present communication infrastructure. An example of this may be seen in the 40 Gigabit Ethernet over twisted pair cabling (40 GBASE-T), which is a potentially new Ethernet standard that will require cabling and connectivity to have a bandwidth of approximately 2 GHz. At this point in time there are no officially published standards concerning this technology. However, today's extensive use of RJ45 connectivity in communication networks can mean that there will be a desire or a need to implement 40 GBASE-T over networks which would be compatible with the RJ45 standard in at least some cases.
One of the key technical challenges is designing a connectivity solution that sufficiently minimizes the near end crosstalk (NEXT) between wire-pairs across the usable 2 GHz bandwidth. The 4:5-3:6 wire-pair combination is particularly challenging as the NEXT present in an RJ45 plug is the highest due to the 3:6 wire-pair splitting around and straddling the 4:5 wire-pair. FIG. 1 illustrates the NEXT performance of an RJ45 plug for pair combination 4:5-3:6 up to 2 GHz. Marker 1 identifies the NEXT at 100 MHz to be −38.1 dB which is about equal to the low plug requirement for a Category 6A RJ45 plug. Marker 2 identifies the NEXT at 100 MHz to be −39.5 dB which is about equal to the high plug requirement for a Category 6A RJ45 plug. The majority of jacks which implement known two-stage compensation techniques are usually tuned to optimize NEXT performance up to 500 MHz when those jacks are mated to an RJ45 plug which is within the low and high plug limits show in FIG. 1. However, the inherent time delay between the crosstalk originating within the plug and the compensation network within the jack can pose a limitation to extending the optimized NEXT performance of the jack beyond 500 MHz.
The time delay is a result of the physical distance between the plug and the compensation arrangement within the jack. If, for example, a time delay of 25 ps (picoseconds) between the plug crosstalk and the jack's compensation is assumed, the simulated NEXT performance of the 4:5-3:6 wire-pair combination will fail a proposed NEXT specifications, as shown in FIG. 2, for the high plug conditions over at least some of the frequency range (the high plug performance of the plug/jack connector combination come near, and in some cases above, a specified maximum NEXT at or above 500 MHz). Note that the exemplary time delay of 25 ps is relatively optimistic in terms of positioning the compensation from the plug crosstalk. However, if the time delay is decreased to a value below 25 ps, the plug/jack system performance would still come close to the specified maximum, leaving the possibility of the plug/jack combination NEXT exceeding the that maximum due to manufacturing tolerances. The exemplary proposed NEXT specification is an extension of the Category 6A component NEXT requirement up to 2 GHz as detailed in Table 1 below.
TABLE 1Frequency (MHz)4:5-3:6 NEXT Loss (dB) 1 ≦ f ≦ 25052.5-20log(f/100)250 ≦ f ≦ 500 44.54-20log(f/250) 500 ≦ f ≦ 100035.5-20log(f/500)
The limitation recited in Table 1 highlight the need for improved connectivity capable of operating above 500 MHz and being compatible with the RJ45 standard in at least some cases.
Note that while the proposed NEXT specification is described as an extension of the Category 6A component NEXT requirement up to 2 GHz, this discussion should be interpreted as non-limiting as this is not the only potential NEXT specification contemplated by the current specification. Principles disclosed in this specification and embodied by the present invention may be applied to any potential NEXT requirements as set forth by any standards bodies now or in the future.